A transient response improvement method of grid-connected converter current proportional repetitive control

Abstract

The invention discloses a transient response improvement method of grid-connected converter current proportion repetitive control in the field of grid-connected converter, which comprises the following steps: 1) determining error threshold value and determining error threshold value according to the magnitude of system steady-state error under single proportion control; 2) selecting an output control quantity, and selecting wheter to update that output control quantity of the repetitive controller according to the absolute value of the error; When the absolute value of error is less than the error threshold, repetitive control is introduced, and the repetitive control algorithm is executed according to the current error, and the output control quantity of the repetitive controller is updated. On the other hand, the error signal input to the repetitive controller is shielded, and the output control quantity of the repetitive controller is not updated. The invention greatly reduces the periodic jump of the output current in the transient process caused by the different response speed of the grid-connected converter and the grid-connected converter when the grid-connected converter adopts the proportional repetitive control, and can be used in the converter control.

Description

technical field [0001] The invention relates to a grid-connected converter, in particular to a current control method of the grid-connected converter. Background technique [0002] At present, there are mainly proportional-integral (PI) controllers, proportional resonant (PR) controllers and repetitive (RC) controllers that are widely used in the current control of grid-connected converters. The PI controller algorithm is the simplest, but it cannot track the AC volume in the natural coordinate system without static error, so it is mostly used in the control of the synchronous rotating coordinate system. At this time, multiple trigonometric function calculations are required, which increases the control System complexity. The PR controller can only realize the non-static tracking of the AC volume at the resonant frequency in the natural coordinate system. For converters such as active filters, since the command current usually contains signals of multiple frequency componen...

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Problems solved by technology

[0003] Since the RC control is essentially a delay control, in order to ensure the response speed of the system, it is usually used in parallel with the proportional (P) controller. The difference in response speed between the P controller and the RC controller makes there be coupling between the two, resulting in During the transient process, the grid-connected current is prone to periodic jumps, which will not only affect the quality of the output current during the transient process, but also may bring a greater impact to the system, especially when the command current changes greatly. The phenomenon is more obvious

[0004] One solution in the prior art is to limit the error input to the RC controller, but it is necessary to select the limit value according to the output of the RC controller in a steady state, and observe the RC controller in the simulation The steady-state output of the RC controller is more convenient, but it is necessary to use debugging software or other means to observe the steady-state output of the RC controller in the experiment, which makes it difficult to determine the limit value by using the experimental method

In addition, the output of the RC controller in the steady state changes with the change of the operating conditions, which brings great difficulties to the selection of the limit value

[0005] Another solution in the prior art is to implement dynamic delay processing on the command signal by introducing a dynamic delay processing module to reduce the error peak value accepted by the RC controller. The time constant is related, which makes the design of dynamic delay beats more complicated

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